/*
 Copyright 2020 The GoPlus Authors (goplus.org)

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
*/

package asttest

import (
	"os"
	"path"
	"syscall"
	"time"
)

// -----------------------------------------------------------------------------

type memFileInfo struct {
	name string
}

func (p *memFileInfo) Name() string {
	return p.name
}

func (p *memFileInfo) Size() int64 {
	return 0
}

func (p *memFileInfo) Mode() os.FileMode {
	return 0
}

func (p *memFileInfo) ModTime() (t time.Time) {
	return
}

func (p *memFileInfo) IsDir() bool {
	return false
}

func (p *memFileInfo) Sys() interface{} {
	return nil
}

// MemFS represents a file system in memory.
type MemFS struct {
	dirs  map[string][]string
	files map[string]string
}

// NewMemFS creates a MemFS instance.
func NewMemFS(dirs map[string][]string, files map[string]string) *MemFS {
	return &MemFS{dirs: dirs, files: files}
}

// ReadDir reads the directory named by dirname and returns
// a list of directory entries sorted by filename.
func (p *MemFS) ReadDir(dirname string) ([]os.FileInfo, error) {
	if items, ok := p.dirs[dirname]; ok {
		fis := make([]os.FileInfo, len(items))
		for i, item := range items {
			fis[i] = &memFileInfo{name: item}
		}
		return fis, nil
	}
	return nil, syscall.ENOENT
}

// ReadFile reads the file named by filename and returns the contents.
// A successful call returns err == nil, not err == EOF. Because ReadFile
// reads the whole file, it does not treat an EOF from Read as an error
// to be reported.
func (p *MemFS) ReadFile(filename string) ([]byte, error) {
	if data, ok := p.files[filename]; ok {
		return []byte(data), nil
	}
	return nil, syscall.ENOENT
}

// Join joins any number of path elements into a single path,
// separating them with slashes. Empty elements are ignored.
// The result is Cleaned. However, if the argument list is
// empty or all its elements are empty, Join returns
// an empty string.
func (p *MemFS) Join(elem ...string) string {
	return path.Join(elem...)
}

// -----------------------------------------------------------------------------

// NewSingleFileFS creates a file system that only contains a single file.
func NewSingleFileFS(dir string, fname string, data string) *MemFS {
	return NewMemFS(map[string][]string{
		dir: {fname},
	}, map[string]string{
		path.Join(dir, fname): data,
	})
}

// -----------------------------------------------------------------------------
